They played together in the states, as well. People who go see RHCP don't care about the openers. It's just a gesture, putting your friends on the bill. I'm sure Keith has been friends with the RHCP dudes for decades at this point.

I've seen them headline twice in the last ten years, one time supported by Mars Volta pre-Comatorium and the other time some random Mike Watt improvisational act which the guitarist of rhcp jammed with for the entire set.

There's a point when you hit a point where no one gives a shit about the openers. It's smart to simply not play that game if you get in that situation. I saw Iron Maiden in the late 90's and of course, as is tradition - both support acts got bottled off..

...Except in this case, the support acts in question? Slayer and Entombed.

The hipster side of the RHCP audience is probably all over 'em. The stoner side WILL be all over OFF! after they see Keith's dreads. The parents will go "OH MY! WHAT IS THIS! The bassist isn't funk influenced at all!"